The field of the invention is that of micro-instrumentation, that is, articulating, hand-held, instruments used in micro-surgery, electronic micro-assembly and like applications, for grasping, cutting, punching out, probing and the like.
The invention is particularly advantageous for endoscopic, or minimally invasive, surgery, but is also advantageous in other applications for micro-instrumentation.
Prior art devices are disclosed in U.S. Pat. No. 5,152,790 to Honkanen et al. and U.S. Pat. No. 5,219,357 to Honkanen et al. These patents disclose endoscopic instruments such as shown in FIG. 1A, using effector tips using one or two jaws, for example, jaw 5 in FIG. 1, rotatably mounted on a pivot 6 mounted on a fixed outer tip 7, rotated by an actuating link 3 driven reciprocally by a drive shaft 2, the entire structure being supported by an extension shaft 1 from a handle assembly with a fixed portion 8 and a movable portion 9 linked to and from which the drive shaft 2 is manipulated. A feature of the inventions in the patents is the employment at jaw 5 of a recess 4 off the pivot center 6 to accommodate and absorb force from the distal end of an actuating link 3 connected to jaw 5 by retaining pin 41. This approach improved over traditional scissor-type linkages by minimizing the width of the structure that pushes the jaw closed around the pivot and by minimizing the shear force on a retaining pin 41 or its counterpart in scissor-type linkages.
Although this prior art device has advantages in strength and form factor over the traditional endoscopic instrument, it has limitation in the mechanical advantage achievable in a limited area. The single pivot and retainer pin placement must remain within the envelope of the outer tip at the risk of exposure to tissue which might jam or break the components. Both the limited joint strength and mechanical advantage of the single pivot design limit how small the distal tip can be made and still remain functional and safe.